Why Eyeballs Don’t Freeze At Subzero Temperatures

In A Nutshell

If our hands, toes, noses, and other body parts are susceptible to freezing and getting frostbitten, it might seem unusual that our eyeballs can survive the cold totally unprotected. But, unlike other bodily extremities, the eyes are constantly pumped with a strong supply of warm blood—even in the coldest situations. Furthermore, our eyes are nestled rather deeply in our heads where bone, tissue, and fat also help keep them warm. Essentially, it’s virtually impossible for the eyes to freeze as long as they are inside a warm, functioning body.

The Whole Bushel

Any time the weather drops below freezing, people quickly don their heavy coats, scarves, and other layers. Yet, for the most part, no one worries about keeping their eyes warm. Even Inuits, Siberians, and Antarctic explorers, who regularly wear Michelin Man–esque clothing, leave their eyeballs exposed. If anyone does put on glasses or goggles, it is mostly to protect their eyes from snow glare or wind—not from the cold. So, what is it exactly about the eyeball that seems to make it immune from freezing?

Although it seems to defy logic that the wet, soft tissue of the eye wouldn’t immediately freeze when the thermometer drops below 32 degrees Fahrenheit, in truth, the explanation is quite simple. Our eyes don’t ice over because they are almost entirely encased in our warm, well-regulated heads. They are positioned more than halfway inside our noggins and protected by insulating bone, muscle, fat, and eyelids.

Making the eye even less likely to freeze is the fact that it’s filled with numerous blood vessels which continually heat it up with the hot blood from our bodies. In fact, the primary blood source to the eye is the ophthalmic artery, which is a branch off the same, deep artery that supplies the brain. When in cold surroundings, the body diverts even more blood to the brain (and other vital organs) which, in turn, helps keep eyes even warmer.

Because tears are saltwater, they are also resistant to freezing; however, they can solidify in extreme cold and possibly “gum up” the eyelids. Even so, the eye itself will be unaffected. Basically, our eyes will only naturally freeze after our bodies are dead and cold.

That being said, it is technically possible to freeze the eye through unnatural means. There is a medical procedure known as retinal cryotherapy, which uses liquid nitrogen to freeze a portion of the eye for the purpose of treating retinal breaks and detachments.